God knows! It's not easy interpreting Augustine on this matter, especially given that he was so clearly rather messed up on the whole subject. Probably something to do with his mother. I don't think he would regard sexual arousal as a sin, but he would regard it as inevitably accompanied by concupiscence. This is pretty standard Platonic stuff. It goes back the Phaedrus, where Plato talks about the three parts of the soul - reason (nous), spirit (thymos), and appetite (epithymia). He uses the famous metaphor of the chariot, where reason, the charioteer, directs the two horses, spirit and appetite. The idea is that you need spirit and appetite to do anything, but they have to be properly guided by reason, or chaos and misery will follow. So that's what it means to have an ordered soul. This idea was developed by the Neoplatonists, who loved hierarchies more than anything. Gregory of Nyssa extended the hierarchy to include God. On his view, spirit must direct appetite, reason must direct spirit, and God must direct reason. That is the secret to a happy life. I think Augustine basically repeats this sort of idea. I did my master's thesis on this in Gregory of Nyssa, so that's one thing I do more or less know about, at least! It probably is older than Leibniz, but as far as I know, it wasn't really explicitly argued for by anyone before him. Don't forget that it was controversial in Leibniz' day and afterwards. Leibniz devotes much of the Theodicy to arguing for this position, and I think most people remained unconvinced - hence Voltaire's famous lampooning of the idea in Candide, and his hectoring against it in his poem on the Lisbon earthquake. I don't know - that's a question for Luther experts. I suspect it was when he met Cajetan, who refused to countenance the possibility that Luther was right, and simply demanded that he recant. Luther had initially assumed that the church authorities would agree with him, but this meeting convinced him that he had been badly mistaken: far from regarding him as an ally, the Pope would condemn him as an opponent. Matthew 26:64. Now, he doesn't say you're not allowed to enjoy it - just that you're not allowed to be lustful. Or something. At any rate, the notion that Adam and Eve did not sleep together before the Fall is very ancient. I think it's universal among the church fathers (some of whom, notably Irenaeus, thought that Adam and Eve were actually children). I don't know if they inherited this belief from Judaism. As far as I know there's no explicit reason for it in the Hebrew - don't forget that the church fathers almost universally disregarded the Hebrew and took the Septuagint to be the inspired text - but Jerome certainly shared this opinion, and he was one of the few to accept the Hebrew. I suppose it's just a natural inference from the way that we told, in 3:24, that Adam and Eve were driven out of the garden, and then immediately told, in 4:1, that they slept together and had children. What do you mean, what is my opinion? On what matter, precisely?